(a) Technical Field
The present disclosure relates to a device and a method of 6-step controlling an inverter of a motor driving system. More particularly, it relates to a device and a method of a 6-step control of an inverter of a motor driving system, which applies a voltage to a motor by applying a 6-step control scheme that uses an input voltage of an inverter to improve output efficiency of the inverter and the motor.
(b) Background Art
In general, a motor driving system for driving a motor includes, as illustrated in FIG. 1, a power supply device for an inverter or a battery 100, configured to supply a direct current voltage to the inverter, a main relay 102 switched for application of the direct current voltage to the inverter 200, the inverter 200 configured to receive the direct current (DC) voltage when the main relay 102 is operated, and convert the received direct current voltage to an alternating current (AC) voltage, and a motor 300 (e.g., three-phase alternating current motor) driven by the alternating current voltage applied from the inverter.
The inverter is configured to generate the direct current voltage input from the power supply device for the inverter or the battery into the alternating current voltage by on-off controlling a switching device (e.g., turning the switching device on and off) through pulse width modulation (PWM), and supply the generated alternating current voltage to the motor for driving the motor. In particular, when the alternating current voltage is supplied from the inverter to the motor in 6-steps by an operation of the inverter, it may be possible to reduce a current consumed by the motor under the same output condition. The supply of the voltage to the motor in the 6-steps may improve efficiency of a system of an environmentally-friendly vehicle, such as an electric vehicle, a hybrid vehicle, and a fuel cell vehicle, in which the motor is mounted, and provide a fuel efficiency improvement effect, as well as improve output and efficiency of the inverter and the motor.
A developed related art discloses a control device and a control method for a motor driving system that include a control configuration switched between a pulse width modulation (PWM) control mode and a rectangular wave voltage control mode. Another related art discloses an AC motor driving controller that includes an overmodulation PWM controller configured to calculate a d-axis voltage instruction and a q-axis voltage instruction in which a voltage amplitude exceeds a peak value of a triangular waveform carrier. The above described related art are technologies for estimating a torque using values detected by a current sensor and a position sensor and motor currents (Id, Iq), and using the estimated torque for controlling feedback of the torque, but have disadvantages described below.
First, since it may not be possible to use a current control loop when the 6-step control is applied, a mode switch (e.g., overmodulation control⇄6-step phase control) technique having no discontinuity is additionally required, and a voltage vector phase calculator configured to estimate a torque is required to be additionally developed.
Second, since the related art uses a closed-loop torque control scheme through estimation of a torque, a high accuracy torque estimator with a satisfied level is additionally required, and a high accuracy loss map is required to estimate a torque using a phase voltage and a phase current.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.